Influence of Vacuum Conditions on Epitaxially Grown Permalloy Films

Abstract

Permalloy films (83 wt% Ni-17 wt% Fe) epitaxially grown on (100) NaCl were examined in the electron microscope before and after beam annealing. An ultra-high vacuum system with an ultimate vacuum of 10−10 Torr and a vacuum system with an ultimate vacuum of 10−6 Torr were used for the evaporation. Films at 10−5 Torr were prepared in both systems to rule out the influence of the vacuum system on the films. Evaporation rates were adjusted to either 30 Å/sec or 14 Å/min. Electron micrographs and electron diffraction patterns showed that the films ranged from polycrystalline for films evaporated at 30 Å/sec and 10−5 Torr to single crystalline with grains of several millimeters diameter for films evaporated at 30 Å/sec and 10−9 Torr. The crystallographic misorientation varied widely in films which were partially single crystalline and amounted to only a few degrees over areas up to ⅛-in. diameter for films which exhibited perfect single-crystal electron diffraction patterns.

Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20

“…53 The existence of twin boundaries in the Py is a signature of high deposition rate which has been observed previously in evaporated 9,54 and electro-deposited 5 films and studied in detail using TEM. [54][55][56] It can be seen that these dots at 23 • also appear in the dcMS deposited film but with very small intensity. This indicates that the fraction of twin boundaries is much lower in the dcMS deposited film.…”

Electron Microscopy

“…; single crystals between 450°to 700°C. Baltz (22) made a similar study, producing both polycrystalline films and single crystals of a Ni-17% Fe alloy. Vook (220) prepared films of oriented single crystals of tin on cleaved NaCl substrates and examined them for dislocations.…”

“…The combined procedures of electron diffraction and microscopy have been used by others to investigate epitaxial growth (22,419), the dendritic crystallization of an amorphous Ge-Te alloy (492), the orientation of an A1203 surface layer which bridged etch pits in an aluminum foil (126), and the crystalline nature of lithium films (141)• Schoening and Baltz (408) studied twinning in annealed single crystal Ni-Fe foils by these methods. The sharp Kikuchi patterns, observed by Vook (469) indicated a very high degree of crystal perfection in ultrahigh vacuumdeposited tin films.…”